Method of making stable cupric



United States Patent METHOD OF MAKING STABLE CUPRIC HYDROXIDE William H.Furness, Haddonfield, N. J., assignor to Copper Research, a corporationof New Jersey Bio Drawing. Original No. 2,666,688, dated January 19,1954, Serial No. 224,840, May 5, 1951. Application for reissue January18, 1956, Serial N0. 560,053

5 Claims. (Cl. 23-147) Matter enclosed in heavy brackets II] appears inthe original arent but forms no part of this reissue specificafion;matter printed in italics indicates the additions made by reissue. Y

The object of this invention is to provide a simple, inexpensive methodfor making stable cupric hydroxide, with a by-product of sodiumsulphate, by means of a controlled, indirect reaction between coppersulphate and sodium hydroxide.

It is known that stable, separable cupric hydroxide cannot be made bydirect reaction between copper sulphate and sodium hydroxide. Thecombination of these two chemicals results in the formation of agelatinous, inseparable sludge of blue cupric hydroxide which rapidlychanges to a useless sludge of black cupric oxide.

Because of the lack of a simple, inexpensive method of manufacture,cupric hydroxide has not heretofore been generally available forcommerce in the large quantities required for use as a fungicide inagriculture, for antifoiiling ship bottom paints, and other similarpurposes.

In my process, pure, stable cupric hydroxide is made from coppersulphate and sodium hydroxide in the following manner:

Step l."Dissolve 380 parts trisodium phosphate (Naa'PO412H2O) using onlyenough water to afford complete solution at room temperature.

Step 2.Place the trisodium phosphate solution of step 1 in a tank oflarge size compared to the volume of the solution; for example, a 100gallon tank if the volume of solution prepared under step 1 is onegallon.

Step 3.To the trisodium phosphate solution in the tank add 250 partscopper sulphate (CuSOrSHzO) dissolved in the minimum quantity of Waterrequired for solution at room temperature. Mix by stirring.

Step 4.-Add to the contents of the tank a solution containing 80 partssodium hydroxide (NaOH), in a concentration of about 80 gm. per liter atroom temperature. Mix by stirring.

Step 5.Add a second solution as in step 3.

Step 6.Add a second quantity of sodium hydroxide as in step 4.

Continue the process by adding successive alternate quantities of coppersulphate and sodium hydroxide until the tank is nearly full. Notrisodium phosphate is employed other than the original quantityspecified in step 1.

When the tank is nearly full, the process is stopped at a pointcorresponding with step 3, that is, after the addition of coppersulphate, and the precipitate is permitted to settle. The supernatantliquid is then drawn off for recovery of sodium sulphate, which at thispoint is the only chemical in solution.

As the volume remaining in the tank is greatly reduced by removal of thesupernatant sodium sulphate solution, the step procedure may be resumedby adding caustic soda, as in step 4, followed by copper sulphate as instep 3, repeatedly until the tank is again nearly filled, when settlingand decantation are again carried out.

The step process is continued until the insoluble cupric quantity ofcopper sulphate hydroxide, resulting from the intermittent alternateadditions and reactions of copper sulphate and sodium hydroxide, nearlyfills the tank after settling. At this stage the process is stopped at apoint corresponding to step 4, that is, with a final addition of thequantity of sodium hydroxide specified in that step. The entire contentsof the tank is then fed to 'a filteron which the cupric hydroxide iscollected; the filtrate, containing the original quantity of trisodiumphosphate, in solution, is returned to the mixing .tank, where theprocess of adding alternate quantities of copper sulphate and sodiumhydroxide may be repeated indefinitely as described.

The following chemical formula is oifered as an indication of probablereactions which occur repeatedlyduring the process as new additions ofcopper sulphate and sodium hydroxide are made:

CUSO4+ Na3PO4 CuNaPOa-l-NazSOs 2NaOH+CuNaPO4=NasPO4+ Cu OH) 2 As thetime element of the chemical reactions involved in the process is verysmall, and no appreciable increase of temperature occurs, the alternateadditions of copper sulphate and sodium hydroxide may be made at briefintervals, and large quantities of cupric hydroxide and sodium sulphateare thus accumulated in a short time.

While my method may be used to make single batches of cupric hydroxide,I prefer to employ the step method described, in which only a relativelysmall and fixed quantity of trisodium phosphate or copper sodiumphosphate alternatively are present. Copper sodium phosphate isdifficult to remove by settling or filtration on a large scale, whilethe small quantities present at intervals in the step process arecarried down with the rapidly settling accumulation of cupric hydroxide,and do not interfere with the decantat'ion of the supernatant liquidcontaining the sodium sulphate in solution.

The action of trisodium phosphate on copper sulphate in aqueous solutionis such that all of the copper contained in a molecular equivalent ofcopper sulphate is precipitated by the addition of less than a molecularequivalent 05f trisodium phosphate. For example, if 250 gms. oftrisodium phosphate (NasPO412H2O) are added to 250 gms. copper sulphate(CLISO45H20) in aqueous solution, all of the copper will be precipitatedand the water will show a neutral reaction with phenolphthalein. Anyadditional amount of trisodium phosphate (NaaPOalZI-IzO) up to a totalof 380 gms. will react with the precipitated copper, the water remainingneutral.

The nature of the copper precipitate varies with the I amount oftrisodium phosphate added but all such precipitates are converted tocupric hydroxide by the addition of a molecular proportion of sodiumhydroxide, the trisodium phosphate being regenerated in the amountoriginally used in each instance. While I prefer to use trisodiumphosphate in the proportion of 380 gms.

(N33PO4 1 21-120) to 250 gms. copper sulphate (CuSOrSI-IzO) because a 98parts cupric hydroxide Cu(OH)2, 142 parts of sodium sulphate (Na2SO4),and 194 parts of trisodium phosphate (Na3PO4), removing the cuprichydroxide by filtration and repeating the process by adding 250 gms.copper sulphate i (CUSO45H2O) to the filtrate, followed by 80 gins.caustic soda (NaOH) to produce a second 98 gms, cupric hydroxide.

2. The method of making cupric hydroxideand sodium sulphate from coppersulphate and caustic soda by adding trisodiumphosphate to a coppersulphate solution in suflicient quantity to precipitate all of thecopper contained therein as copper sodium phosphate, and to react withall of the sulphate radical of the copper sulphate to form sodiumsulphate in solution, and then adding to the mixture a suflicientquantity of caustic soda to convert the insoluble copper sodiumphosphate to insoluble cupric hydroxide and trisodium phosphate andremoving the cupric hydroxide by filtration; thereafter adding to thefiltrate sufficient copper sulphate to react with the trisodiumphosphate present therein to form copper sodium phosphate and sodiumsulphate and removing the insoluble copper sodium phosphate byfiltration and recovering the sodium sulphate from the filtrate bycrystallization or evaporation.

3. The cyclic process of making cupric hydroxide from copper sulphateand caustic soda in which molecularly equivalent and equal unit massesof copper sulphate and caustic soda are added repeatedly and alternatelyto a volume of water containing a quantity of trisodium phosphatesufficient to convert all of the copper contained in the unit of coppersulphate first added to insoluble copper sodium phosphate and sodiumsulphate, and in which each addition of copper sulphate is followed by amolecularly equivalent quantity of caustic soda which reacts with thecopper sodium phosphate resulting from the preceding step to form cuprichydroxide and trisodium phosphate, the repeated alternate additions ofthe unit masses of copper sulphate and caustic soda resulting in anaccumulation of cupric hydroxide and sodium sulphate in the mixture,from which part of the cupric hydroxide 4 is removed from time to timeby filtration at any interval following an addition of caustic soda whenthe phosphate radical is in solution, and part of the accumulated sodiumfate as copper sodium phosphate, then adding to theaqu e ous mediumcontaining the precipitated copper sodium phosphate a stoichiometricallyequivalent quantity of caustic soda to convert the copper sodiumphosphate to cupric hydroxide, and recovering the cupric hydroxide.

5. A method for making stable cupric hydroxide which comprises reeatedly adding first copper sulphate and then caustic soda instoichiometric proportions for producing cupric hydroxide to a volume ofwater containing a quantity of trisodium phosphate sufficient to convertall of the copper in each addition of copper sulfate to. in-

soluble copper sodium phosphate, and recovering thecupric hydroxideafter an addition of caustic soda.

References Cited in the file of this patent or the original patentUNITED STATES PATENTS 1,800,828 Furness Apr. 14, 1931 2,168,985Gulbrandsen a Aug. 8, 1939 2,525,242 Rowe Oct. 10, 1950 2,532,308Hoffman Dec. 5, 1950 FOREIGN PATENTS 410,940 Great Britain May 31, 1934510,082 Great Britain July 24, 1 939 OTHER REFERENCES Mellor:Comprehensive Treatise on Inorganic and Theoretical Chemistry, vol. 3,1923, pages 143' and 144.

